Peru’s presidential candidate Keiko Fujimori for “Fuerza Popular” party, gestures after voting in the runoff round in Lima on June 5, 2016

Lima (AFP) - Peruvian presidential candidate Keiko Fujimori will hold out until the last ballot is counted in a photo-finish run-off election, her spokesman said Thursday, dashing front-runner Pedro Pablo Kuczynski's hopes she might concede.

Four days after the election, 99.99 percent of the ballots have been counted, but the country still doesn't know who its next leader is -- and it was unclear how long it would take.

With the count nearly complete from Sunday's vote, ex-Wall Street banker Kuczynski led Fujimori by a razor-thin margin: 50.12 percent to 49.88 percent.

But electoral authorities were still waiting for seven results sheets to arrive from a remote valley in the Amazon rainforest.

The results were being transported partly by river, with a security escort to keep them safe from the drug traffickers and guerrilla fighters hiding out in the region.

A small number of ballots -- 0.41 percent of the total -- have also been challenged in court for smudges, improper markings or other issues, keeping alive Fujimori's hopes that she can still close the gap of less than 40,000 votes between her and Kuczynski.

The electoral court is working its way through the challenged results sheets one by one, but there is no clear timeline for how long the process will take.

The head of the electoral authority was to give a press conference Thursday, after the final results arrive, with more details on the endgame.

Pollsters and statisticians say it would be all but impossible for Fujimori, the daughter of jailed ex-president Alberto Fujimori (1990-2000), to pull off a victory.

"Can Peru beat Germany 7-3 in a football match? It's not mathematically impossible, but it's not going to happen," said Farid Matuk, the former head of the national statistics institute, by way of illustration.

Kuczynski's camp has taken to declaring him the virtual president-elect on a daily basis.

"You all know what the margin is. There's no reason for it to change," one of his spokesmen, congressman-elect Gilbert Violeta, said Wednesday.

"Like all Peru, we want this to end soon."

- Jungle vote -

Peru, a nation of 31 million people, is one of Latin America's fastest-growing economies, and both candidates are right-leaning, market-friendly, US-educated politicians from immigrant families.

Kuczynski, 77, has said he won't declare victory until the official verdict is in.

Fujimori, 41, has hunkered down in her campaign headquarters.

Her campaign is hoping she will make up ground on the challenged ballots and win heavily in the still-uncounted Amazon region known as VRAEM, the acronym for the Apurimac, Ene and Mantaro River Valleys.

Advisers say she is strong in the isolated and lawless region thanks to her tough stance on crime and her father's campaign to wipe out the leftist rebels of the Shining Path movement, whose remnants are still hiding out in the valley's dense rainforest.

Some Peruvians fondly remember Alberto Fujimori for his populist streak, his ruthless crack-down on the Shining Path and his management of a strong economy.

But his legacy has also been heavy baggage for his daughter. His violent decade in office ultimately landed him in prison for 25 years for massacres by an army death squad.

- Divided government? -

Famed for its ancient Incan cities high in the Andes mountains and its fusion-fueled cuisine, symbolized by the refreshing raw fish dish ceviche, Peru is a major exporter of gold, copper -- and cocaine.

Economic growth slowed under outgoing leftist President Ollanta Humala, from 6.5 percent when he took office in 2011 to 3.3 percent last year.

Kuczynski, son of a Jewish doctor from Germany, studied at Oxford and Princeton.

A former economy minister, he has a long career in business and finance.

Fujimori, whose father is the child of Japanese immigrants, was aiming to become Peru's first woman president.

But analysts say she was damaged by a late surge of "anti-fujimorismo" -- though her party won a congressional majority in the first-round vote in April.